1. Field of the Invention
This invention is in the field of scroll fluid devices wherein meshed involute scroll wraps move in orbital fashion relative to each other to effect energy transfer by positive fluid displacement in chambers generated between the scroll wraps during operation of the device.
2. Description of Prior Art
The generic term "scroll fluid device" is applied to the well-known arrangement of meshed, involute spiral wraps that are moved along curvilinear translation paths in orbiting fashion relative to each other to produce one or more fluid transporting or working chambers that move radially between entrance and exit zones of the device. The scroll devices may function as pumps, compressors, expanders, or motors, depending upon their configuration, the drive system, and the nature of energy transfer between the scroll wraps and the fluid moving through the device.
Scroll devices, including their principle of operation, are fully described by way of example in the following U.S. Pat. Nos. 3,874,827 to Niels O. Young; 3,560,119 to W. Busch et al.; and 4,141,677 to Weaver et al. The descriptions contained in the aforementioned patents, to the extent that they generally describe the theory of operation and typical structural arrrangements of scroll fluid devices is herein incorporated by reference.
In scroll fluid devices, it is usually imperative that the scroll wraps be maintained in an established phase relationship in respect of their angular orientation relative to each other. Essentially, once the wraps are meshed in an established or desired position in which the involute wraps are disposed in a certain relative angular position relative to each other, this position must be maintained during the operation of the scroll device to maintain sealing contact between wrap flanks (sidewalls) and to maintain the design configuration of the fluid chamber that effects positive displacement of fluid moving through the scroll device (if a pump) or that constitutes the working chamber of the device (if a motor). While minor excursions from the design set point may be tolerated in some designs, generally, the relative angular position of the scroll wraps must be maintained during the operation of typical scroll fluid devices.
In the prior art, the relative angular orientation of the scroll wraps is maintained typically by Oldham couplings that maintain the meshed scroll wraps in torisonally coupled relationship that permits relative orbital movement while restricting relative rotation between the wraps. The aforementioned patents described typical Oldham couplings.
A problem encountered in prior art devices is that typical Oldham couplings are often imprecise, require lubrication under higher loads and speeds of operation, and they are subject to rotational imbalances when the scroll wraps are co-rotated together as a spinning unit.
While some approaches have been taken in the prior art to eliminate such disadvantages, typically the solution leads to other disadvantages, including complexity, structurally weaker designs, or restrictions against certain degrees of movement of the scroll wraps that might be desired or necessary for optimized performance of the device.